Lost circulation in drilling engineering is a phenomenon that the drilling fluid leaks from the well bore into the formation. Lost circulation often happens in the drilling or trip process, and is a challenge frequently encountered in the oil and gas exploration and drilling process. At present, commonly used plugging methods include bridge plugging and cement plugging. Cement plugging is to plug the fractures and solution cavities in the leak formation, but it is difficult to control the initial setting time and final setting time, the construction risk is high, and problems such as quick leakage of high-density cement slurry or quick setting of quick-setting cement may occur easily, resulting in downhole accidents such as jamming of drilling tools and causing severe economic loss. Bridge plugging is mainly to prepare plugging slurry from plugging materials at a certain ratio, and plug the fractures and pore channels with the plugging slurry, so that the leak formation is sealed under bridging, bracing, bonding, plugging, and filling effects. A key technique for bridge plugging lies in whether the distribution of particle size of the bridging agent matches the diameters of the leak channels. However, in the drilling process, sometimes the formulation of the bridging agent can't be selected and determined because the widths of fractures and the sizes of the pores in the leak formation can't be ascertained; consequently, the uncertainty of successful operation is increased, the success ratio of plugging is compromised, and the resultant plugged formation doesn't have high strength and may leak again owing to the high differential pressure in the well drilling process.